Hangfire recorder



March 9, 1948. H SMH-H ET AL 2,437,276

HANGFIRE RECORDER Filed Aug. 26 l1941 4 Sheets-Sheet l March 9,- 1948.

I-I. SMITH ET AI.

HANGFIRE RECORDER Filed Aug. 26, 3.941 4 Sheets-'Sheet I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I l I I I I I I I I I I I I ITI VET-LICITE Har-Schal 'mII-I lames v DuI-LhaTI-I Navman K TurI-Lbull BY QW/@MMM I ATTORNEYS March 9, 1948. H. SMITH ET A1.

HANGFIRE RECORDER Filed Aug. 26, 1941 4 sheets-sheet 5 Herschal Smith damals V. Dunham NnrmanKTLwT-Lhull BYa/@WJ Qui ATTORNEYS March 9, 1948.

H. SMITH TAL 2,437,276

HANGFIRE RECORDER Filed Aug. 26, 1941 4 Sheets-Sheet 4 In VEmtnrE HErSc-LEI Emi t h dames Vjjunham NnrmanKTurI-Lhull ATToR Evs 5 Patented Mar. 9, 1948 UNITED STATES .LNT GFFICE HANGFERE Application August 26, lillil, Serial No. @108,334

(Cl. 23e-36.5)

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 22 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, Without the payment to us of any royalty thereon.

This invention relates to the measurement ci the characteristics of ammunition and to apparatus for recording those characteristics.

An object of this invention is to measure the time elapsed between the actuation oi the trigger of a projectile ring device and the emergence of the projectile from the muzzle of the device.

Another object of this invention is to have smooth Working electronic tube apparatus for producing a permanent record of the hangfire characteristics of ammunition.

Another objectv of this invention is to measure and record the hangiire characteristics of aromunition by electrostatic means sensitive to the charges produced subsequent to the ring of the ammunition.

Another object of this invention is to incorporate a control circuit in a hangnre measuring circuit so that all of the operating personnel may be behind the firearm when it is discharged thus eliminating possible danger to the health and life of the operating personnel.

Another object of this invention is to perform a: hangre test on blank ammunition.

Another object of this invention is to measure hangflre of ammunition with a limited number of: persons.

Another object` of. this invention is to have hangre measuring apparatus which may be made portable by one skilled in the art so that hangre measurements on any caliber Weapon in the fie-ld might be made.

Another object of this invention is to have hangflre. measuring apparatus in which one recorder may be, used to record the hangfire characteristics of diierent caliberl ammunition with facility, thus reducing installation costs.

Another object of this invention is to provide a recorder for recording events.

With the foregoing and other objects in View, thisA invention resides in the novel arrangement and. combination of elements necessary for the measurement of hangre in the manner described, it being understood that changes in the precise embodiment of the invention herein disclosed may bernade Within the scope of what is claimed Without departing: from the spirit of the invention.

Practical embodiments of the arrangements utilized are disclosed by Way of illustration in the accompanying drawings,l wherein:

Fig. 1 discloses the disposition of electrical cir'- euit elements and mechanicalA elements.

Fig. 2 is a plan view of the recorder which is shown schematically in Fig. 1.

Fis. 3 is a side View of the Fig. 2.

Fig. l is a view taken substantially on line 4 4 or" Fig. 3.

Fig. 5 is a View taken substantially on line 5 5 of Fig. 3.

Fig. o is a view taken substantially on line 5 5 of Fig. 2.

Fig. '7 is an elevation, partly in section, of the manual means for rotating the drum shaft.

Fig. 'la is a horizontal sectional View of the means disclosed in Fig. 7.

Fig. 8 is a View taken substantially on line 8 8 of Fig. 3.

Fig. 9 is a View taken substantiallyA on line 9 9 of Fig. 3 and discloses the arrangement of the apertures 832, 5320i, etc., in the end of the drum.

rihe principle of operation of this hangiire recorder resides in the fact that the gases which escape from the muzzle of a gun are electrically charged at a potential diiierent from themuzzle potential. This fact is disclosed in Patent 2206, 92'?, granted to Norman K. Turnbull and James V. Dunham on July 9, i940, and also in Patent 2,146,723, granted to James V. Dunham and Ernest R. Reche] on February 14, 1939.

Referring to Fig. l., the numeral 2 indicates the firearm in which the ammunition to be tested is fired. The gun is grounded electrically as indicated at 2. A collector l is placed near the end of the muzzle ofthe gun. This collector is charged electrically by the gases which emerge from the muzzle. The collecter may be constructed in the manner shown in Fig. 1 of Patent 2,266,927, re ieri-ed to above. The lead Wire 3 is coupled tothe grid of the gaseous discharge tube d, which is referred to in the art as a thyratron tube, through the switch 552i and coupling capacitor The grid ci the thyratron tube l is biased by the direct current source t and associated resistors l and 8 so that the tube #l passes practically no current when normal voltages are applied to the plate of the tube. The resistor 8 is a potentiometer bridging the source t, both being grounded at their ends distant from the grid, as at t.

The capacitor is connected and cathode of the tube l and the principal func,- tion of capacitor Q is to limit high frequency surges so that harmful voltages are not applied to the grid of the thyratron tube f3. The variable po` tentiometer resistor 3 allows the bias voltage to recorder shown in between the grid be varied at will. The resistors 'I and 8 also serve to dissipate any charges which might accumulate on the collector I, the capacitor 5, or the capacitor 9 so that spurious action of the tube 4 is prevented.

The cathode of the thyratron tube 4 is connected to ground I3' through the resistor I2 and the primary winding I of transformer T. The sec ondary winding II of transformer T is connected to an impulse counting circuit to be described later, through the capacitor 26.

The trigger of the iirearm 2 is actuated by a magnetic trigger operating mechanism shown schematically in Fig. 1 and designated as I4. The magnetic trigger operating mechanism may be of any of the well known types and may be of the type described in the copending patent of Norman K. Turnbull and Herschel Smith, No. 2,331,942, October 19, 1943. The ammunition in the rearm 2 is adapted to be iired upon energization of the magnet windingr I4. An electronic rectifier I5 of any of the well known types is connected across the magnet winding I4 so that the voltage induced in the `winding I4 due to a decaying eld in the magnet has little or no effect on the source of power supplylng the magnet winding.

The output current of the tube 4 passes through the primary winding I0 of the transformer T through resistor I2 to ground at I3'. The secondary winding II is connected across terminals of a spark recorder I8, through ground connections I3 and I8. The resistor I2 serves to limit the flow of the output current through tube 4.

The mechanical details of the spark recorder are disclosed in Figs. 2-9 and are to be described later. In general, the recorder consists of a rotatable metallic drum IUD, grounded at I8', Fig. 1. Means are provided to hold a record sheet about the periphery of the drum. A carriage |60 is mounted for translation adjacent and axially along the drum and a stylus I8, which may be a tungsten wire, is mounted upon this carriage. Circuit connection is made with the stylus such that when a high voltage is induced in the circuit, a spark jumps between the end of the stylus and the drum, and forms a record mark upon the aforesaid sheet. A motor |03 is adapted to rotate the drum and to move the stylus carriage axially therealong, in timed relation. A magnetically operated clutch on the carriage is energizable to connect and disconnect the carriage with the motor. Thus, the carriage is moved only when the clutch is energized. l

The power supply for the cathode-plate circuit of the tube 4 is largely supplied from a charged capacitor 22. The capacitor 22 is charged from the A. C. source I9 through the rectiers 23 and 2|. The net eiect of the two tubes 20 and 2I is to produce a full wave rectified output. The capacitor 22 is charged through the resistors 23 and 24. The voltage which the capacitor 22 will assume when the relay R3 is deenergized is determined largely by the value of the resistors 23, 24, and 25. In order to energize the plate of the tube 4, it is necessary that the winding of relay R3 be energized. The winding of relay R2 is connected in parallel with the winding of relays R1 and R3 so that relaysRl, Rz and R3 are always energized simultaneously. The normally open contacts of relay R2 are connected in parallel to the resistor 23 so that the resistor 23 is short circuited when the relay Rz is energized. Thus, upon energization of relays R2 and R3, the capacitor 22 which has been pre- 4 viously charged, discharges through the platecathode circuit of the tube 4 and since the resistor 23 is short circuited, the D. C. output potential distribution is altered in a direction to tend to make the available power output greater. The current in the output circuit of the tube 4 is in the nature of a pulse and the greater portion of the energy of that pulse is due to the energy which was originally stored in the capacitor 22.

The pulse of current in the output circuit of the tube 4 is partially transformed in the output circuit of the transformer T. The output or secondary winding I I of transformer T is coupled to the grid-cathode circuit of a thyratron type tube 21 through the capacitor 26 and the indicated ground connections. The resistor 28 and potentiometer 29 tend to limit the iiow of gridcathode current in the tube 21. The source of D. C. potential 30 and adjustable potentiometer 29 produce a variable bias voltage source for the grid of tube 21.

The winding, 3|, of a counter is connected in the plate circuit of the tube 21. The impulse counter is of the type which registers one impulse each time the magnetizable operating member is displaced in a given direction due to the action of magnet 3l. Such impulse counters are well known in the art. Also, the switching element 33 attached to the magnetizable member 32 is adapted to open the pair of contacts 33. The contacts 33 bridge the parallel circuit formed by the resistor 34 and the capacitor 35. The capacitor 36 is charged from the A. C. source 3'I through the rectiiying tubes 38, 39 and the inductor 43 in the nature of a choke coil. The resistor 4I stabilizes the output of the rectiiier because of the load imposed on the rectii'ler. The gas discharge tube 21 is biased by the potentiometer 29 so that normally no current ows in the plate circuit. When a pulse is transmitted to the grid of the tube 21, a current flows through the winding 3l and shunt or short path through switch 33 around the parallel circuit 34, 35. Due to the action of the operating member of the device 32, an impulse is registered on the impulse counter and simultaneously the parallel elements 34 and 35 are inserted in the plate circuit. Due to the fact that the pulse transmitted to the grid of the tube 21 is of short duration and due to the fact that the current passed at 33 independently of the elements 34 and 35 causes an appreciable drop of potential in the plate voltage of the tube, the tube 21 will return to its normal non-conducting condition after every pulse.

The trigger actuating magnet I4 is energized by the current which iiows through the gaseous discharge tube 42. Commutator switches designated as On and Off control the firing of the tube 42. These switches are separate from one another but are rotated in synchronism with the recording drum. Both switches are closed once per revolution of the recorder shaft and the "OP switch is closed approximately .01'0 sec. after the On switch closes. The tube 42 is normally biased by the source of D. C. current 43 so that normally no current ows in the output circuit of tube 42. 'I'he resistor 44 tends to limit the ow of grid-cathode current. The source of D. C. voltage 45 is connected through the Cn switch and is of sumcient value to cause the tube 4'2 to become conducting when a pulse is transmitted from this source to the grid of the tube, and while the normal plate potential is maintained, as will be explained. The resistor 46 tends to limit the flow of `current from the `source 45.

vcontacts of relay R4 and of relay R5, the source of current 52-53 48, the trigger-actuating magnet I4 to the cathode of tube 42. The current will also be augmented by discharge of condenser 48 as elsewhere described. Also, since the capacitor 49 is connected in parallel to the resistor 41, the capacitor 49 will acquire a charge and a potential as indicated in Fig. 1 due to the potential drop across the resistor 41. The capacitor 49 is connected directly across the plate and cathode of tube 42 through the Off switch. Since the 01T switch closes a short time after the On switch has closed and opened, the reverse D. C. potential supplied by the capacitor 49 through the "Oif switch is suiiicient to extinguish the arc in tube 42. Thus the On and Off switches eifect a recurring current flow in the tube 42 and trigger-actuating magnet I4.

The plate voltage supply for the tube 42 operates in a manner similar to the plate voltage supply for the tube 4. The capacitor 48 supplies most of the energy necessary to actuate the triggeroperating mechanism. The capacitor 48 is charged through the resistor 5| when the tube 42 is not being supplied. The relay R4 when energized closes the plate supply circuit to the tube 42. The relay R5 which is operated simultaneously with relay R4 short circuits the resistor 5| so that a higher voltage may appear across the loading resistor 41. The capacitor 48 is charged through the full wave rectifier comprising the tubes 52, 53 from transformer T2.

Actuation of the trigger switch serves to energize the relays R1, R2, R3. R4 and R5 simultaneously, with the result that the plates of tubes 4 and42 are charged although at the moment neither of the respective tubes is conducting. Also energization of relay R1 causes the stylus magnets, |15, |1| in Fig. 3, to be energized through a rectifier comprising tube 54, inductor 55 and capacitors 56a and 51a. The resistor 58a is made adjustable and tends to limit the current which flows through the stylus magnets |10, |1I. Energization of the stylus magnets |10, I1| allows the tungsten point I8 to move parallel to the axis of the recorder. Thus, the trigger switch serves to (1) control the ring of the firearm, (2) control the operation of the recorder input circuit and (3) control the movement of the tungsten electrode I8.

The function of the zero shot switch is to allow the firearm to be discharged once only.

The switches 56, 51, 58 serve to connect the electrical elements associated with the rearm to the hangre measuring circuit proper. It appears obvious that the switches 56, 51, and 58 may be made in the nature of selector switches so that any one of a plurality of firearms might be connected to the hangiire measuring circuit proper.

The switch 59 serves to connect the A. C. source E0 to motor |03.

Description of recorder structure The recorder has a drum |00 upon which a piece of recording paper (not shown) may be held'by the two axially disposed split resilient bands |0l, |02 and it is understood that other types of means may be employed to hold the recording paper on the drum.

The drum |00 is adaptedto be 4driven by the synchronous motor I 03 through a clutch |05 (Fig. 6) on the left hand side ofthe drum in Fig. 2. Gears |08 (on motorshaft |06), |23 (on shaft |25), on shaft |26 and worm |28 vare permanently interconnected and are 'driven by the synchronous motor. Collar '|21 is xed on shaft |25 and has mounted thereon `a housing |28 for a spring pressed pin |29 which has a knurled end |30 and its other end |-3| adapted to fit in any one of a plurality of equally spaced apertures |32, |3211, etc., forming a concentric series in the end wall of the drum (Fig. 9); the spring |33 acting on shoulder |34 normally biases the head I3| in the direction of the hole |32 and is adapted to fit in any one of the spaced apertures.

The drum driving shaft |25 is free to rotate with respect to the drum |00 when the clutch |05 is in disengaged position; the drum has bearings |35, |36 disposed on each of its ends through which the shaft |25 passes.

Commutator type switches |31, |38 designated as On and Off switches are rigidly and adjustably mounted on the shaft |25 by set screws |39, 40. The switches are similar in structure and a description of switch |31 will suilce to explain the details of switch |38; Switch |31 (Fig. 5) comprises a rotatable cylinder |4| which is made of insulating material and has a metal commutator contact bar v|42 embedded therein; a pair of metallic brush contact members |43 having electrical leads attached thereto are adapted to be engaged by the metallic bar |42 once per revolution of the cylinder |4|. The set screws |39, |40 allow the bars corresponding to bar |42 to be set in angular spaced relationship to one another circumferentially of the shaft |25 so as to properly time the associated electrical circuits |44, |45.

The shaft |25 is rotatably supported in bearings |46, |41 (Figure 3) which are formed in the spaced members |48, |49 respectively.

The worm |26 is free to rotate in bearings |50, |5I (Figure 2) in the spaced members |52, |53 respectively and has the gear |24 fixed thereon.

As will be more fully described subsequently, it is necessary before a zero shot is made, to index or angularly adjust the drum |00 by hand, with the synchronous motor deenergized. For this purpose there is provided a manual indexing mechanism |04, which is adapted to effect manual rotation of shaft |06 and is operated only when the synchronous motor is deenergized. The synchronous motor shaft |06 is adapted to be held by the inner surfaces of the two-halves |09, ||0 of a split hollow vcylinder (Fig. 7). It is understood that the members |09, 0 may take other forms and shapes asl long as they are adapted to be drawn together by the split surrounding clamp III, the two halves of which are articulated together by pin ||2. An adjustable stop 3 mounted on supporting member |54 serves to limit the downward movement of the manual indexing mechanism and to provide an adjustment for its alignment. A manually operable handle ||4 is adapted to pass through the slotted portion |5 of the clamp |I| and to be pivoted about the pin ||6 which is held by the walls which define the slot. A pin ||1 xedly mounted in the handle is adapted to contact the bottom pair of faces I|8 on the lower member of the clamp ||I. Counterclockwise rotation of the handle ||4 in Figs. 2 and 7 will cause the spaced .laws IIB, |20 of clamp to move closer togather andpthuscanse thefs-plit halves- |09, A| |0 to frictionallygengage the shaftv |06; further such rotation-will cause; the drum to rotate. The split halves |09, ||0 have-anges |2I, |22 which maintain the split halves. in centered relation in Y.

the clamp. Gearsv |08, |23, |25, shaft |25 and worm |26 are permanently interconnected and rotate when the manual indexing mechanism |04 is-rotated.v A spring |||a having its ends disposed in recesses in the spaced portions H9, |20 servesto hold the manual indexing mechanism |04 in a normally disengaged position.

The supporting membersldg, |53, |54, |43, |52 are'bolted to the bed plate |55, the latter being the electrical groundinvolved throughout the system. .Y A housing |55 supported by the supports |49, |53 by bolts |5611, |551) serves to enclose the gears |23, |24, |08.

A carriage |50 is adapted to be moved paralle tothe axial direction of the drum |00 due to the rotation .of worm |26.' The carriage |60 is slidable along the guides |5|, |62 which have their ends xedly mounted tothe supports |52, |53. The worm |25 passes slidably through two spaced :openingsl 60aand 50h in the carriage and is engaged by the worm wheel |65 which is normally free to .rotate about the cylindrical projection |500 on the carriage; flathead screw |60e holds the worm wheel on the carriage but allows rotation of. the worm wheel.

.Rotation of l'the worm .wheel may be prevented by magnetic clutchv means which are now to be described. .The carriage has mounted thereon a pair of magneti-c solenoids |10, |1| by means of angle irons |12, |13 and-associated screws. Each solenoid has mounted von its upper end a magnetic bar- |15 .which extends through an aperture |15l inthe vcarriage and abuts a magnetic ring |11 which is,.concentrically mounted on the worm wheel |55 by means of screws |18. The ring |11 will hereinafter be referred to as the lcontact ring and each one of the magnetic bars |15 will be referred to as a contact bar. The contact ring |11 normally lightly abuts the contact bars but their contact introduces. practically no frictional resistance to rotation of the worm wheel |65. The magnetic attraction between the contact bar and the contact ring, however, is suiilcient when the magnetic solenoids "|10, |1| are energized, to clutch and hold the worm wheel |65 against rotation whereby the carriage moves on its guides itl., |522'- It is understood that one magnetic solenoid maybe used instead of the two solenoids disclosed in the drawings in order to accomplish the purposes of this invention, It is preferable that the material'surrounding thelsolenoids be non-magnetic, except the contact ring and contact bar, so that the solenoid is not magnetically short `cir'cuited andthe full effect ofv the magnetic iield produced is instrumental in stopping the 'worm wheel promptly when the solenoids are energized to thereby translate carriage |55 axially along rods I5! and |52 in timed relation with notation of worm |25.

The stylus holder |50 is pivotably mounted on the carriage block |8| bymeans of the hinge connections |82, |83; oneA part of each hinge is fastened to the stylus holder E50 and the other part of the same hinge is fastened to the carriage block as shown in Figs. 2 and 8. The carriage block 5| has agroove |513 in each end face which are adapted to receive spring `fasteners |85, |86. so that the stylus holder is rigidly held in its operating position. The stylus holder |80 has a centrally g Adisposed. hole |81 through which a metallic Wire I8", preferably'of tungsten, passes vand forms one electrode ofthe spark recorder.

The metallic wire may be frictionally held in the hole |81 lor the wire may be held by a set screw in the stylus holder |85. This arrangementprovides an adjustable spark gap between the stylus holder and the drum.

Holder is made of dielectric material to insulate stylus I8" from carriage 60. The stylus is connected with the external circuit through lead |92, insulated terminal |88, and a lead, not shown, extending from this terminal to the stylus.

An index member |55 is fastened to the fixed supporting member |58 and has a pointed end positioned adjacent the outside periphery of the collar |21 on the drum shaft |25. The periphery of collar |21 is suitably graduated so that the positions of the shaft |25 and switches |31, |38 may be ascertained. Definite markings are made on the periphery of the collar |21 that correspond to the positions in which the On or Off switches are in circuit closing position; these markings are very helpful when making single shot records since in that case an electrical control circuit is connected through one of the switches which must be closed in order that the single shot discharge be produced.

Operation and measurement of hangfre There are essentially three electrical systems involved in the invention and its utilization as disclosed. These comprise, A, a trigger operating system including two alternative operating cir-` cuits, one including a rotary circuit-closing switch i 31 which determines the rate of sustained rapid nre oi the weapon; the other alternate circuit having a manual single shot control; B, a recording system responsive to the discharges of gas incident to firing of'the weapon to operate the recorder icc, and C, a counter system operating the counter 32 coincidentally with, but independently of, the recording system and trigger operating system. It is thought the operation of the counter is simple enough and suihciently apparent to require no extended description.

lin the operation of the firing mechanism, when it is desired to fire a single shot, it is unnecessary to have the drum of the recorder device in rotation, but if it is desired to make a record of the shot, the paper sheet is attached as indicated, and the drum rotated and stopped so as to position the stylus in alignment with the proper line on the sheet, the stylus being adjusted longitudinally to the position to begin a line of recordings, or to form one mark in sequence with those of a line already begun. Before any switches are closed, a round of ammunition is chambered in the firearm conventionally and the Zero shot switch at 55 closed while the trigger switch .is left open. The latter will insure that no accidental electrical operation of the firing mechanism can occur until desired. 'The switches 55, 51 and 58 are closed; the switch 59 in the motor lead open. With the drum proper position for a recording, the On switch |31 will be closed, but the operating plate circuit will be open at relay R4. The biasing potential of the battery 53 will be overbalanced by the potential of battery 45 which maintains the grid at iiring potential, so that the tube will conduct whenever the plate circuit is completed at relay Rd. The Off switch |38 will not be required in this operation.

Due to the functioning of the transformer T2,

while the relays R and'RE are still open the condenser 48 will become highly charged across the resistor I, the resistor 41 passing immaterial current.

For this single shot operation, conditions being as stated, as soon as the triggerswitch is closed, parallel circuits to all of the relays RI, R2, R3, R4 and R5 are closed. The first relay closes a circuit to the stylus magnets of Fig. i and Figs. 3 and 8, which is immaterial for this operation, since no rotation or the drum is required (but will be essential in alternative use of the system for rapid fire to operate the switches iSI-I 33). The second relay closes a by-pass or short circuit around the resistance 23 in the system B which will be described subsequently, Relay R3 closes the plate circuit of system C to be later described. Pickup of relays R5 and R4, respectively, short the resistance 5I and complete the plate circuit to the tube 42. At first, the tube grid being now at a high positive potential, the surge from condenser 48 and the rectied current from the transformer combined are effective at the plate and produce a powerful cathode-plate discharge across the tube, operating the trigger device at I6. Then, with a delay proportional to the value of the inductance at R53, and which will approximate 0.01 second, the relay R5 will open the operating grid circuit from the battery 45, and immediately permit blocking of conduction in the plate circuit by the normal biasing voltage of the battery 43. Completion of loading of the coil at R'will result also in application of the operating voltage of the plate circuit to the cathode in opposition to the negative potential in the lead through the magnet i 4. At the same time the condenser ed discharges through the shorting bypass (around the impedances of R) completed by the lower contacts and blade of the relay. This develops a negative component at the plate and a further positive accretion at the cathode. The reversal of the polarity of the cathode connection and application of inverted potentials at the plate and cathode by the condenser 49 would in themselves be sufficient to block. The combined eiects thus applied to block the tube result in a very abrupt cut-off.

Completion of cutoi'i of the tu-be 42 leaves the relay R6 still energized in a circuit completed through resistance 5I) from the positive lead of the plate circuit through R5 and the leads from and to the firing device Ie, and consequently the tube 42 is maintained in a blocked condition as long as the "trigger and zero shot switches are both closed. The absence of the potentials derived from the condensers 48 and 49, and impedances at 5! and in R6, however, leave the plate circuit ineffective to operate the trigger device at I4, and no further operation of the latter occurs until the zero shot switch or one in the plate circuit is opened and closed again as before mentioned. The firearm mechanism may automatically reload with another round, if it is supplied with belted or magazine ammunition.

Opening of either of the switches mentioned or either of those 5'! and 58 will drop the relay R6 and cause a renewal of the operating charge on condenser 43 and raising of the grid at 'i2 to firing potential.

Closing of either the trigger switch or one of those 5l' or 58 while the zero shot switch is closed without changing the remainder of the circuits, will result in a repeated single shot operation of the firing device I4, as before.

In the alternate or rapid nre operation of the system A, the zero shot switch is kept open, and

the relay RB and its functions are not employed. The motor 03 is kept in operation for driving of the recorder machine parts and for the operation of the On and Oi switches 37 and i253. For system A only these lastv named two switches are involved, and the recorder operation will be described in relation to system B.

In the ring of typical automatic nrearms or machine guns, rates of nre of from say ifty or more for pistols and to 1500 in machine guns are involved, and the frequency of closing of the On switch will in the present instance be depended on to determine the rate of iire, instead of depending on the inherent capability of means in the weapon itself for determining the irequency of ire, The invention is principally intended for testing the capability of automatic loading and firing mechanisms to maintain high rates of fire, means being provided to make the firing dependent on the closing of the plate circuit of tube 42.

In rapid re operation, action at the weapon may be started and stopped by operation of either the trigger switch or one of the switches 51-58 while the motor H13 is operating. But it may be stopped at any time by closing the zero shot switch with the eiect previously described, and consequently also initiated thereafter by opening that switch while the remainder of the switches last named are closed, the On and "Oi switches being in continual operation whenever the trigger switch is closed.

The organization of the parameters is such that the condensers 43 and 438 can become charged to the desired extent in the interval between shots red at a maximum rate and the corresponding intervals in interruption of the plate circuit of the tube 42.

In rapid fire operation, switch 59 is closed and the motor |03 is kept constantly in operation. The grid circuit of tube 42 is closed except at the On switch, and a tube-blocking, snorting or bypass circuit equivalent to that through the lower contacts of R6 when closed is closed by the Off switch alternately with closing of the On switch. The commutator of the Oli switch is adjusted angularly on the shaft |25 in relation to the commutator of the On switch so as to close, say, .01 second after closing of the On switch.

In effect, the operating potential is maintained at the plate for a suitable period before the blocking potential is applied by the OE switch, but firing of the tube is caused only by closing of the On switch. Consequently, while the trigger switch and switches 5l and 58 are closed and the motor operating there will be a continual intermittent closing of the On switch, ring a shot at I4 each time, followed almost immediately by a blocking potential applied to the tube by closing of the 01T switch, the rate of such nre being dependent on the speed of the motor and the transmission ratio connections in the gear train of Fig. 1,

During operation of the motor, the drum ID@ is rotated in synchronism with the switch I 3l', so that a particular line on the attached sheet is aligned with the stylus I8 each time the plate circuit is closed, and the stylus is also moved longitudinally as previously described, so that the stylus is stepped along the line on the paper at each rotation of the drum and ring of the arm 2. Thus, when any recording impulse is transmitted through the stylus for a shot actually manifest at the muzzle of the weapon, a respective discrete record will be formed in an 1ii orderly series 'on'the record sheetI 'This recording impulse is provided for in system C now to be described. Y

In system C thertube 4 has its plate supplied as beforerdescribed in such manner that when the grid potential is raised properly above cutoi a discharge occurs in the cathode-plate circuit for which the rectified current from 2li-2| and the charge on the condenser 2'2 are available. It has been'explained in detail how the parameters are organized to establish the plate supply when the relays R2 and R3 are closed, which is a constant condition when the trigger switch Vis closed to produce the rapid fire operation. Raising of the grid potential to fire the tube is eiected by utilizing the charge collected by the ring l on each shot, inV conjunction with the adjusted critical potential supplied by the source 6 and resistances 1 and 8. When the plate circuit pulse occurs, the pulse thereby induced in the secondary of the transformer Ill- II acts to produce the recording action at the stylus I8 and also to transmit a pulse to the operating tube 2l of the counter system before described in suiicient detail.

' It having been before explained how the stylus is positioned on the same line each time the On switch is closed, such closure involving a respective shot or failure of the arm, and how the stylus is also stepped horizontally, it is apparent that pulses transmitted to thetstylus will produce discrete marks in orderly series, any omissions in which will appear as a blank in a line of marks on the paper record on the drum. The adjustment and functioning of the drum operating and lstylus moving means have been before described with suicient detail so that the utilization of the mechanism will be understood.

It is preferable to control rapid re operation by means of the trigger switch, because incident to the opening of Vthe latter the relay Rl is opened, which frees the clutch of the recorder, so that the stylus is not moved longitudinally of the drum, and the motor and drum may be kept in operation when no firing is carried Von without disturbing the continuity of the record when rapid ring is resumed by closing of the trigger switch. This relay RI opens and closes a special magnet operating circuit through the rectifier 54 smoothing LC` device 55--56 and adjusted resistor 53a, before referred to.

The record appears as a row of dots on the waxed paper. The dots are Yseparated by about le inch and form approximately a straight line parallel to the axis of the drum. The zero shot appears ahead of the main group in line with its beginning, Any blank intervals in a line of dots made during the described rapid re procedure will represent hange fires, or the point 'of stoppage in a sustained burst, the causes of which may bevarious, and will be independently determined.

In order to make another record on the same piece of paper the drum is rotated with respect to the On and Off switches by pulling the pinv |29 out of the aperture |32 in the drum, Figs. 2 and 6, rotating the drum with respect to the switches and allowing the spring biased pin 129 to fall into an adjacent aperture l32c. Thus another record may be made on the same piece of waxed paper. The two records will be parallel to one another and parallel to the axis of the drum.

When as many records as desired have been made on a sheet of recording paper, it is removed and laid fiat on a board against a straight edge. With the help of a triangle the extreme dot positionsl are marked (with a line near the edge of the paper) for each group. The zero shot position also is similarly marked.

Since the drum rotates at a constant speed for the continuous fire record, the distance between adjacent marks which are due to the spark discharge is a measure of the elapsed time. For practical purposes that distance is measured along a line perpendicular to a line which is parallel to the axis of the drum and is on the paper. Of course, the path of the recording point is a spiral about the drum; but, since the point advances only inch in each 25 inches of peripheral movement of the drum, the error introduced by making the measurements as described is less than l/iooo of one percent. The distance (in time units) between the extreme shots of the burst gives the group width. The zero shot is measured in the same manner. In our particular apparatus the drum rotates 450 times per minute; its diameter is '7.92 inches. This gives .1866 inch per millisecond for the conversion factor.

We claim:

l. In a system for measuring the characteristics of ammunition propelled from a firearm, electric means for actuating the firing means of the iirearm, a recorder having a rotatable drum, a plurality of electric switches, means for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder, and electric means responsive to the actuation of the switches for energizing and deenergizing said first mentioned electric means.

2. In a system for measuring the characteristics of ammunition propelled from a firearm, a magnet coil for actuating the firing means of the firearm, a recorder having a rotatable drum, a plurality of electric switches, means for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder, and electric means responsive to the actuation of the switches for energizing and deenergizing said magnet coil.

3. In a system for measuring the characteristics of ammunition propelled from a firearm, electric means for actuating the firing means of the rearm, a recorder having a rotatable drum, a plurality of electric switches, means for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder, electric means responsive to the actuation of the switches for energizing and deenergizing said iirst mentioned electric means, and electric means responsive to the actuation of the switches for energizing and deenergizing said indicia producing means.

4. In a system for measuring the characteristics of ammunition propelled from a firearm, a magnet coil for actuating the iiring means of the firearm, a recorder having a rotatable drum, a plurality of electric switches, means for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder, electric means responsive to the actuation of the switches for energizing and deenergizing said magnet coil, and electric means responsive to the 13 actuation ofthe switches for. energizing and deenergizing said indicia producing means.

5. In a system for measuring the characteristics of ammunition propelled from a rearm, electric means for actuating the firing meansv of the firearm, a recorder having a rotatable drum, a plurality of electric switches, means for actuating said switches intimed relation to the rotation of the recorder, electric means responsive to the presence of propelled gases from the ammunition forl producing indicia on the recorder, electric means responsive to the actuation ci the switches for energizing and deenergizing said iirst mentioned electric means recurrently, and electric, means coacting with one of said switches constructed, arranged and adapted to assume an inoperative condition with the rst named means in response to one energization of the rst mentioned electric means.

6.. In a system for measuring the character'- istics of ammunition propelled from a firearm, a magnet coil for actuating the firing means of the firearm, aV recorder having a rotatable drum, a plurality of eiectric switches, means for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of propellent gases from the ammunition for producing indicia on the recorder, electric means responsive to the actuation of the switches for energizing and deenergizing said magnet coil recurrently, and electric means coacting with one of said switches constructed, arranged and adapted with and to said coil to assume therewith an inoperative condition responsive to one energization of the magnet coil.

'1. In a system for measuring the characteristics of ammunition propelled from a firearm, electric means for actuating the iiring means oi the rearm, a recorder having a rotatable drum, a plurality of electric switches, means for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of the propellent gases fromv the ammunition for producing indicia on the recorder, an electric counter coupled to the last mentioned means for recording the number of said indicia, and electric means responsive to the actuation of the switches for energizing and deenergizing said rst mentioned electric means.

8. In a system for measuring the characteristics of ammunition propelled from a firearm, a magnet coil for actuating the firing means of the iirearm a recorder having. arotatable drum, a plurality of electric switches,v means` for actuating said switches in timed relation to the rotation of the recorder, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder, an electric counter coupled to the last mentioned means for recording the number of said indicia, and electric means responsive to the actuation of the switches for energizing and deenergizing said magnet coil.

9. In a system for measuring the characteristics of ammunition propelled from a firearm, electric means for actuating the ring means of the iirearm, a rotatable drum adapted to hold recording paper, a magnetic clutch, a stylus for said recording paper movable through the magnetic clutch, a plurality of electric switches, means for actuating said switches in timed relation to the rotation of the drum, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recording paper, electric means responsive 14 to the actuation of the switches for energizing and deenergizing said first mentioned electric means, and switching meansr for simultaneously energizing said last mentioned means and the magnetic clutch.

10. In a system for measuring the characteristics of ammunition propelled from a firearm, a magnet coil for actuating the firing means vof the firearm,A a. rotatable drum adapted to hold recording paper, a magnetic clutch, a stylus for said recording paper movable through the magnetic clutch, a plurality of electric switches, means for actuating said switches in timed relation tothe rotation of the drum', electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recording paper, electric means responsive to the actuation of the switches for energizing and deenergizing said magnet coil, and switching meansY for simultaneously energizing said last mentioned means and the magnetic clutch.

11. In a system for measuring the characteristics of ammunition propelled `from a rearm, electric means for actuating the firing means of the iirearm, a recorder, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder. and electric means responsive to the indicia yproducing means for energizing the first mentioned electric means.

12. In a system for measuring the characteristics of ammunition propelled from a rearm, electric means for actuating the ring means of the firearm, a recorder, electric means responsive to the presence of the propellent gases from the ammunitionv for producing indicia on the recorder, and electricv means responsive to the indicia producing means for recurrently energizing the first mentioned electric means.

13. In a system for measuring the characteristics of ammunition propelledl from a iirearm, electric means for actuating the iiring means of the rearm, a recorder, electric means responsive to thev presence of propellent gases from the ammunition for producing indicia on the recorder, electric means responsive to the indicia producing means for energizing the rst mentioned electric means, and electric means constructed, arranged and adapted to assume with the first-named means an inoperative condition in response to one energization of the first mentioned electricmeans.

14. In a system for measuring the characteristics of ammunition propelled from a rearm,

electric means. for actuating the firing means of the firearm, a recorder, a magnetic clutch, electric means responsive to the presence of the propellent gases from the ammunition for producing indicia on the recorder, a stylus for the recorder operable through the magnetic clutch, and switching means for simultaneously energizing said first mentioned means and the magnetic clutch.

15. In recording apparatus, an electric circuit, a rotatable drum adapted to hold paper for recording signals transmitted by the said circuit, a rotatable worm, a carriage, a stylus on the carriage, a worm Wheel rotatable on the carriage and adapted to engage the worm, and means responsive to impulses in said circuit for locking he worm wheel against rotation.

16. In recording apparatus, an electric circuit, a rotatable drum adapted to hold paper for recording signals transmitted by the said circuit, a rotatable worm, a carriage, a stylus on the 15v carriage, a worm wheel having some magnetizable materialv and rotatable on the carriage 'and adapted to engage the worm, and magnetic means on the carriage responsive to impulses in said circuit adapted to lock the worm wheel against rotation.

17. In recording apparatus of the character described, a rotatable drumshaft and drum thereon, means to rotate the shaft at constant speed an electrical gun firing circuit including a switch, a re recording device cooperative with the drum surface constructed to respond to a gun discharge, and including a stylus and means to move the stylus longitudinally of the drum, means responsive to each rotation of the drum to actuate the switch, and means to adjust the angular position of the drum on the shaft.

18. In a gunfire recording device, a rotatable drum, means to rotate the same at constant speed closely approximating in revolutions per vminute a maximumv rate of fire of a gun measured inrounds per minute, an electrical 'gunfiring device including a switch and operative'connection between the switch and drum to close and open the v from the Vmuzzle' of the gun, including a' record forming member movable longitudinally ofl the drum, and operative connections between the drum and last'named member.

19. The structure of claim 18 including means to'selectively fix the drum in angular relation to the operative connection between the switch and drum.

20. In recording apparatus, an electric circuit, a rotatable shaft, a drum rotatable thereon, and adapted to support a record sheet thereon, a switch in said circuit, means responsive to each rotation of the shaft for actuating the switch, record forming means connected in said circuit constructed and arranged to form on said sheet a record of pulses transmitted in said circuit said record-forming means including a point member movable longitudinally beside the drum operative to form respective discrete records on said sheet in response to said pulses, means operatively connected to the shaft to progressively move the point member longitudinally of the drum, means operatively connected with vthe drum to enable the adjustment of the recording operation of said record-forming means in relation to the angular position of the shaft, means to rotate the shaft and means coupling the drum for releasing the shaft in selective angular relation thereto.

21.111 a'. recording apparatus 'of the 'character' described, a rotating drum shaft, a relatively ro.

tatable record drum thereon, a parallel rotatable worm shaft geared to the drum shaft, a carriage slidable along the worm shaft, electrical means to connect the worm shaft in driving relation to the carriage and including a switch; means to fix the drum on the drum shaft in selective angular relation thereto, a recording device on the carriage, means for operating the drum shaft, a main control circuitl operatively associated with said switch and means responsive to operation REFERENCES CITED The following references are of record in the le of this patent:

- UNITED STATES PATENTS Y Number4 Name Date 1,241,213 Heisler Sept. 25, 1917 1,489,566 Webster Apr, 8, 1924 1,977,256 Swart Oct. 16, 1934 2,030,794 Horton Feb. 11, 1936 2,056,912 Swart Oct. 6, 1936 2,092,851 Osgood Sept. 14, 1936 2,100,460 Specht Nov. 30, 1937 2,132,264 King Oct. 4, 1938 2,206,927 Turnbull July 9, 1940 2,224,832 Pfister Dec. 10, 1940 2,235,385 Rava Mar. 18, 1941 2,250,102 Klemperer July 22, 1941 2,251,306 Thompson Aug. 5, 1941 2,294,388 Dawson Sept. 1, 1942 2,331,942 Turnbull et al Oct. 19, 1943 FOREC-N PATENTS Number Country Date 22,308 Australia 1929 OTHER REFERENCES Eastman, Fundamentals of Vacuum Tubes," McGraw-Hill Book Co., New York, N. Y.; pages 221-222. 

